Characterization of surface defects on composite sandwich materials based on deflectrometry

This paper presents a new characterization technique to measure and quantify surface defects in composites. During manufacturing of composite sandwich parts, imperfections appear on the skins due to molding parameters such as temperature, pressure and humidity. Recurring imperfections observed on the surface of composites include surface porosities, resin shrinkage and gloss variation. Although several methods to characterize such defects were developed in the past, visual inspection remains widely used in the industry. In this paper, two different types of surface defects often encountered in the composite industry are measured: surface porosities and resin shrinkage. The proposed measurement method uses an optical system based on deflectometry. Unlike other methods, this technique provides real-time mapping of reflected light intensity. It also provides surface curvature variation which is the most relevant criterion for surface appearance analysis. The results further suggest that setting a threshold on a given parameter (e.g. total surface area of porosities per unit area of sample) and using a fully automated procedure would make this approach very efficient for quality control operations of composite parts.